Eli5: Does ash remain ash for eternity?


Does it ever decompose or turn into something? If no, then theoretically, if we burned all dead bodies for trillions of years, would earth eventually run out of supply because there was only ash left, thus life would end? Sorry if this sounds stupid

In: Chemistry

>Does it ever decompose or turn into something

Yes. Ash is what remains after you burn someone.
So oxidized stuff, mostly metal oxides.
The carbon is gone as co2 mostly.

Most of those are at least somewhat solvable in water, and so will get washed into the ground and oceans.

Ash is actually a good fertilizer in ways.

Pretty sure ash is mostly carbon which is decently reactive? And other minerals that would seep into the earth and eventually be soaked away in tree roots and such.

Ash is mostly oxidized minerals. At some point these minerals were rocks or sand before plants or bacteria were able to absorb them. This is how it entered our body in the first place. Ash is actually used as a fertilizer in order to give plants mineral suppliments. Some mineral suppliments for humans are even based on ash which have been purified, although not from human cremation.

Everything will break down eventually into its consituent parts and be “recycled” in one way or another. Besides, the amout of matter you’re talking about is microscopic in comparison to the total mass of all matter on Earth. You might find this article on the BBC website intersting: [Who, What, Why: Is the Earth getting lighter?](https://www.bbc.co.uk/news/magazine-16787636)

No, in many ways.

You can’t burn all the bodies of humans for trillions of years because in 5B years the Sun will be a red giant reaching to the Earth’s orbit and the whole planet will have melted and been consumed by the Sun.

The bodies of all the humans isn’t really a lot of mass. There are 7.2B humans on the planet today, let’s say they weigh a combined total of about 350B kg. The Earth’s surface is 500M km^2. That’s 700kg/km^2 or 7kg/hectare. Normal fertilizer usage is 200kg/ha, so frankly there just isn’t enough human mass on this planet to make any meaningful impact.